Originally Posted by
ala_xfire
The leaking valve covers are most likely the 'vent' covers ( the ones with the hoses connected ).
They come from the factory with MB RTV sealant, there is a thread on here about cleaning them up and installing with new RTV.
WARNING ! Those are aluminum bolts on the vent covers, DO NOT OVERTIGHTEN.
This is a VERY common problem, the rubber valve cover gaskets are usually not a problem, if the bolt torque is correct.
Yes, mostly it is those smaller covers although the valve covers are showing some too. Is it possible that because the covers are leaky the pressure is decreased causing the knocking?